In testing high density and high speed electrical devices such as IC and LSI circuits, a high performance contact structure such as a probe contact assembly having a large number of contactors must be used. The present invention is directed to a contact structure and a probe contact assembly using such a contact structure. The present invention is also directed to a production process of the contact structure and the probe contact assembly. The contact structure is used in combination with a test system for testing and burning-in IC and LSI chips, semiconductor wafers, packaged semiconductor devices, printed circuit boards and the like.
In the case where semiconductor devices to be tested are in the form of a semiconductor wafer, a semiconductor test system such as an IC tester is usually connected to a substrate handler, such as an automatic wafer prober, to automatically test the semiconductor wafer. Such an example is shown in FIG. 1 in which a semiconductor test system has a test head 100 which is ordinarily in a separate housing and electrically connected to the test system with a bundle of cables 110. The test head 100 and a substrate handler 400 are mechanically as well as electrically connected with one another with the aid of a manipulator 500 which is driven by a motor 510. The semiconductor wafers to be tested are automatically provided to a test position of the test head 100 by the substrate handler 400.
On the test head 100, the semiconductor wafer to be tested is provided with test signals generated by the semiconductor test system. The resultant output signals from the semiconductor wafer under test (IC circuits formed on the semiconductor wafer) are transmitted to the semiconductor test system. In the semiconductor test system, the output signals from the wafer are compared with expected data to determine whether the IC circuits on the semiconductor wafer function correctly.
Referring to FIGS. 1 and 2, the test head 100 and the substrate handler 400 are connected through an interface component 140 consisting of a performance board 120 which is a printed circuit board having electric circuit connections unique to a test head's electrical footprint, coaxial cables, pogo-pins and connectors. The test head 100 includes a large number of printed circuit boards 150 which correspond to the number of test channels (test pins) of the semiconductor test system. Each of the printed circuit boards 150 has a connector 160 to receive a corresponding contact terminal 121 of the performance board 120.
A “frog” ring 130 is mounted on the performance board 120 to accurately determine the contact position relative to the substrate handler 400. The frog ring 130 has a large number of contact pins 141, such as ZIF connectors or pogo-pins, connected to contact terminals 121, through coaxial cables 124.
As shown in FIG. 2, the test head 100 is positioned over the substrate handler 400 and connected to the substrate handler through the interface component 140. In the substrate handler 400, a semiconductor wafer 300 to be tested is mounted on a chuck 180. In this example, a probe card 170 is provided above the semiconductor wafer 300 to be tested. The probe card 170 has a large number of probe contactors (such as cantilevers or needles) 190 to contact with contact targets such as circuit terminals or pads in the IC circuit on the semiconductor wafer 300 under test.
Electrodes (contact pads) of the probe card 170 are electrically connected to the contact pins (pogo-pins) 141 provided on the frog ring 130. The pogo-pins 141 are also connected to the contact terminals 121 of the performance board 120 through the coaxial cables 124 where each contact terminal 121 is connected to the corresponding printed circuit board (pin cards) 150 in the test head 100. Further, the printed circuit boards 150 are connected to the semiconductor test system through the cable 110 having, for example, several hundreds of inner cables.
Under this arrangement, the probe contactors 190 contact the surface (contact target) of the semiconductor wafer 300 on the chuck 180 to apply test signals to the semiconductor wafer 300 and receive the resultant output signals from the wafer 300. As noted above, the resultant output signals from the semiconductor wafer 300 under test are compared with the expected data generated by the semiconductor test system to determine whether or not the IC circuits on the semiconductor wafer 300 performs correctly.
FIGS. 3-5 show examples of conventional contact structure and probe contact assembly using the contact structure. The contact structures in these examples are implemented by the same assignee of the present invention and have advantages and disadvantages. In these examples, identical reference numbers are used to denotes the same or similar components.
FIG. 3 is a cross sectional view showing an example of conventional probe contact system formed with a pogo-pin block 130, a probe card 260, and a contact structure having a contactor carrier 22 and contactors 30. In an application of semiconductor test, the contact structure is positioned, for example, over a semiconductor device such as a silicon wafer 300 to be tested. When the silicon wafer 300 is moved upward, the lower ends of the contactors 30 contact with contact pads 320 on the semiconductor wafer 300 to establish electrical communication therebetween.
In this example, the contactor carrier 20 is comprised of a system carrier 22 and a top retainer 24. The contactor carrier 20 is made of dielectric material such as silicon, polyimide, ceramic or glass. The system carrier 22 supports the top retainer 24 as well as creates a predetermined distance or space between the top retainer 24. The top retainer 24 and the system carrier 22 respectively have through holes for mounting the contactors 30.
Each contactor 30 has a top spring 32 having an upper end 33 oriented in a vertical direction, a bottom spring 36 having a lower end 35 oriented in a direction opposite to the upper end 33 and a body portion 37 between the top spring 32 and the bottom spring 36. At both sides of the body portion 37, stoppers 34 are provided to securely mount the contactor 30 on the contactor carrier 20. The top spring 32 is zig-zaged or provided with at least one diagonal beam portion between the top end 33 and the body portion 37 for producing a resilient contact force. The body portion 37 has a flat square shape as a whole having the stoppers 34 at both sides as noted above. The bottom spring 36 is zig-zaged or provided with at least one diagonal beam portion between the body portion 37 and the lower end 35 for producing a resilient contact force.
The probe card 260, pogo-pin block 130 and contact structure are mechanically as well as electronically connected with one another, thereby forming a probe contact assembly. Thus, electrical paths are created from the lower ends 35 (contact point) of the contactors 30 to the test head 100 through the cables 124 and the performance board 120 (FIG. 2). Thus, when the semiconductor wafer 300 and the probe contact assembly are pressed with each other, electrical communication will be established between the DUT (contact pads 320 on the wafer 300) and the test system.
The pogo-pin block (frog ring) 130 is equivalent to the one shown in FIG. 2 having a large number of pogo-pins to interface between the probe card 260 and the performance board 120. At upper ends of the pogo-pins, cables 124 such as coaxial cables are connected to transmit signals to printed circuit boards (pin cards) 150 in the test head 100 in FIG. 2 through the performance board 120. The probe card 260 has a large number of electrodes 262 and 265 on the upper and lower surfaces thereof.
When assembled, the top ends 33 of the contactors 30 contact the electrodes 262 of the probe card 260. The electrodes 262 and 265 are connected through interconnect traces 263 to fan-out the pitch of the contact structure to meet the pitch of the pogo-pins in the pogo-pin block 130. The top springs 32 of the contactors 30 produce resilient contact forces against the electrodes 262. When the contact structure is pressed against the semiconductor wafer 300, the bottom springs 36 of the contactors 30 produce resilient contact forces against the contact pads 320.
The conventional technology shown in FIG. 3 has a drawback in that the size of the zig-zaged spring of the contact limits the pitch or pin count of the contactors. Further, because the interconnection between the contactors and the probe card, or between the contactors and space transformer (not shown), is done through spring contacts, high reliability of interconnection is unavailable. Further, because of the relatively complicated structure, it is time consuming to adjust the planarity and alignment of the contact points of the contactors.
FIG. 4 shows another example of conventional probe contact assembly in which a contact structure is configured by a contactor carrier 20 and a plurality of contactors 30. In this example, the contactor carrier 20 is comprised of a system carrier 22, a top plate carrier 24, an intermediate plate carrier 26, and a bottom plate carrier 28. The contactor carrier 20 is made of dielectric material such as silicon, polyimide, ceramic or glass. The system carrier 22 supports the top, intermediate, and bottom plate carriers with predetermined space therebetween. The top plate carrier 24, the intermediate plate carrier 26 and the bottom plate carrier 28 respectively have through holes for mounting the contactors 30.
Each contactor 30 is composed of an upper end (base portion) 33, a diagonal beam (spring) portion 32, a straight beam portion 36, a lower end (contact portion) 35 and a return portion 37. Preferably, stoppers 34 and 38 are provided to each contactor 30 to securely mount the contactor 30 on the contactor carrier 20. The diagonal beam portion 32 diagonally extends between the upper end 33 and the straight beam portion 36.
The diagonal beam (spring) portion 32 of the contactor 30 functions as a spring to produce a resilient force when the upper end 33 contact the probe card 260 and the lower end 35 is pressed against the contact target. The straight beam portion 36 extends downwardly between the diagonal beam portion 32 and the lower end 35. The upper end 33 and the lower end 35 function as contact points to establish electrical communication with other components. The lower end 35 functions to contact with a contact target such as the contact pad 320 on the semiconductor wafer 300.
The return portion 37 runs upwardly from the lower end 35 in parallel with the straight beam portion 36. In other words, the return portion 37 and the straight beam portion 36 constitute a space (gap) S therebetween at about a position inserted in the through hole of the bottom plate carrier 28. This structure ensures a sufficient width with respect to the through holes on the bottom plate carrier 28 and allows flexibility when deforming the contactor 30. This is effective when the contactor is pressed against the contact target.
The conventional technology shown in FIG. 4 has a drawback in that it is not easy to assemble the contactors on the contactor carrier. Further, because the interconnection between the contactors and the probe card, or between the contactors and space transformer (not shown), is done through spring contacts, high reliability of interconnection is unavailable.
FIGS. 5A and 5B show a further example of conventional contactor structure where FIG. 5A is a cross sectional view and FIG. 5B is a bottom view of thereof. The contact structure is formed of contactors 30 and a contact substrate 20 mounting the contactors 30. The contact substrate 20 also functions as a space transformer. The contactor 30 has a conductive layer 35 in a finger (beam) like shape. The contactor 30 also has a base 40 which is attached to the contact substrate 20. An interconnect trace 24 is connected to the conductive layer 35 at a bottom surface of the contact substrate 20. Such a connection between the interconnect trace 24 and the conductive layer 35 is made, for example, through a solder ball (not shown).
The contact substrate 20 further includes a via hole 23 and an electrode 22. The electrode 22 is to interconnect the contact substrate 20 to an external structure such as a probe card or IC package through a wire or lead. In this example, adhesives 45 are used to bond the contactors 30 to the surface of the contact substrate 20 at the sides of the set of the contactors 30 as well as at the corners formed by the silicon base 40 and the contact substrate 20. Because of the spring force of the beam like shape of the contactor 30 mounted in a diagonal direction on the contact substrate 20, the end of the conductive layer 35 produces a resilient contact force when the semiconductor wafer 300 is pressed against the contact structure.
The conventional technology shown in FIG. 5 has a drawback in that since a line of multiple beams of the contactors 30 is produced in a comb like shape through an anisotropic etching process, such a comb like series of contactors are not suitable for an array pattern of contact probe.